Table 1 Examples of natural polymers and their structural and morphological descriptors
From: What can we learn from biodegradation of natural polymers for regulation?
Natural polymer | Source | Structure | Morphology | Properties | References |
|---|---|---|---|---|---|
Starch | Produced by most green plants for energy storage, and (major) ingredient in wheat, potatoes, maize (corn), and rice, banana peels | Polysaccharide; branched amylopectin and linear amylose chains; Weak α-glycosidic bonds | Granular shape, alternating amorphous and semi crystalline layers | White, tasteless and odourless powder; mostly insoluble in cold water or alcohol | Polman et al. [24], Kögel-Knabner [25] |
Cellulose | Plant cell walls rice hulls cotton | Polysaccharide (C6H10O5)n; D-glucose units; stronger β-glycosidic linkages; linear (unbranched) chain with degree of polymerization (DP) values of several hundred to many thousand depending on the origin and treatment | Crystalline (but small fraction amorphous) | Tasteless and odourless; hydrophilic; insoluble in water and most organic solvents | Polman et al. [24], Klemm et al. [26], Kulkarni et al. [27] |
Hemicellulose | Plant cell walls | Heterogeneous group of polysaccharides; pentosen (xylose, arabinose) and hexosen (glucose, mannose, galactose), and can contain acidic forms, β-(1,4)-linked backbones; branched consists of shorter chains—500–3,000 sugar units | Random, amorphous structure with little strength | Water solubility depends on type and degree of substitution | Kulkarni et al. [27], Scheller and Ulvskov [28], Ebringerová et al. [29] |
Pectin | Plant cell walls citrus peels apple pomace banana peels | Linear polysaccharide, galacturonic acid interrupted with L-rhamnose units, α-glycosidic bonds few hundred to about one thousand units per molecule, | Gelling depending on type and structure | Hydrophilic; soluble in water, gel in aqueous solution if dissolved at higher temperature | Kulkarni et al. [27], BeMiller [30], Acquavia et al. [31] |
Lignin | Plant cell walls wood and bark | Consists of the aromatic coniferyl, coumaryl and sinapyl alcohols, bound together by C–O–C or C–C linkages; about 50% of these are the β-O-4 aryl ether type | Amorphic three-dimensional polymer | Insoluble lacks in hydrolyzable linkages | Polman et al. [24], Datta et al. [32], Zhang et al. [23], Tyagi et al. [33] |
Cutin | Plant cuticle tomato waste | Polyester polymer consisting of omega hydroxy acids and their derivatives composed of various characteristic long-chain (C16Â and C18) alkanoic acids (most of them saturated) substituted by hydroxy, carbonyl, and epoxy groups | Lipid, waxy polymer amorphous and flexible three-dimensional | Insoluble in organic solvents; water resistant (hydrophobic, lipophilic) | Riederer and Schonherr [34], Briggs [35], Acquavia et al. [31] |
Natural rubber | Elastomer made from latex, a sticky, milky plant sap | Cis-1,4-polyisoprene; allylic C-H bonds in each repeat unit | Strain crystallization | Insoluble in water | Rose and Steinbüchel [36], Greve [37], Konno [38], Shah et al. [39] |